Arc welding on a horizontal surface inherently presents a problem in retaining the molten slag and metal at the edge of the horizontal surface of the workpiece to form the metal bead flush with the edge. The arc welding process, wherein the molten slag and metal are kept submerged beneath its flux burden, is usually propagated smoothly over horizontal surfaces until the inevitable edge, or corner, of the work surface is reached. It takes little imagination to visualize that when the molten slag and metal, of which the bead is formed, reach the edge of a workpiece surface, the precipitous vertical drop from the edge provides an undesirable path for runoff of both molten slag and metal. A barrier to prevent escape of these materials over the edge of the workpiece is required.
There is no necessity for analysis of the various forms of runoff bars and tabs evolved in the prior art. It is sufficient to describe the present problem of retaining molten slag and metal at the external edge, or corner, of a workpiece.
Not all edges of workpieces are simple, straight lines, and, of course, the length of the edges vary from workpiece to workpiece. There are workpieces with curved edges which also need to be guarded against the escape of molten welding materials until they solidify. Workers in the art have clamped lengths of angle iron along the edges of the surface of the workpiece upon which the flux overburden has collected to provide a mold body for the molten materials of the arc at the workpiece edge.
As simple as the problem is of providing mechanical support for flux at the workpiece edge with a length of angle iron, the speed of production is limited by the preparation of these angle irons of suitable lengths and contours to match the lengths and contours of the workpiece edges.
What is needed, is a dam structure which can be connected to the welding head itself, to move with the arc, providing constant support for a body of flux far enough ahead of the arc to prepare for the continuous molding function, and far enough behind the arc to provide time for welding metal to solidify into its bead. It is not necessary for the dam structure to actually be attached to the welding head; however it is necessary for the two to maintain a common orientation. It simply appears that the welding head would make a convenient station at which the dam structure could be mounted and articulated to cooperate efficiently with the welding operation at the arc. Certainly, the dam, or barrier, structure will have to engage the vertical surface beneath the edge of the working surface to form retention structure for the flux overburden. It is highly desirable that the engagement between the dam structure and the vertical surface not result in sliding the structures over each other. A sliding movement would cause flux movement which must be stationary with respect to the molten slag and metal, while the metal is solidifying into its bead form.